Kavli Affiliate: Roberto Maiolino
| First 5 Authors: Gareth C. Jones, Gareth C. Jones, , ,
| Summary:
Recent photometric surveys with JWST have revealed a significant population
of mysterious objects with red colours, compact morphologies, frequent signs of
active galactic nucleus (AGN) activity, and negligible X-ray emission. These
‘Little Red Dots’ (LRDs) have been explored through spectral and photometric
studies, but their nature is still under debate. As part of the BlackTHUNDER
survey, we have observed UNCOVER_20466, the second most distant LRD known
(z=8.5), with the JWST/NIRSpec IFU. Previous JWST/NIRCam and JWST/NIRSpec MSA
observations of this source revealed its LRD nature, as well as the presence of
an AGN. Using our NIRSpec IFU data, we confirm that UNCOVER_20466 contains an
overmassive black hole. However, our observed Balmer decrements imply
negligible dust attenuation, resulting in a much lower Hbeta-based bolometric
luminosity and Eddington luminosity (~10%) than previously found. Lyman-alpha
emission is strongly detected, implying f_esc,Lya~30%. The extremely high
[OIII]4363/Hgamma ratio is indicative of not only AGN photoionization and
heating, but also extremely high densities (ne~10^7cm-3), suggesting that this
black hole at such high redshift may be forming in an ultra-dense protogalaxy.
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